Seals of the type to which the present invention relate are not new per se. Typically these seals are mounted in the bore of the bearing housing and have a sealing surface which rests against a cylindrical surface of the machine part supported in the bearing bushing and an auxiliary sealing element disposed between the open end of the bearing bushing and a shoulder of the machine part mounted therein. A seal of this general type is shown, for example, in West German Patent No. 2,908,713. The seal illustrated in this patent tends to expand conically when it is pressed onto a shoulder of the machine part supported in the bearing and thus, the sealing action of the sealing lip resting against the bearing decreases.